1. Field of the Invention
This invention relates to pulse radar apparatus and is concerned more particularly with apparatus employing frequency diversity to maximise target detection.
2. Prior Art
The performance of maritime radar apparatus, whether sited on the coast or on a ship or in an aircraft, is severely restricted by sea-clutter returns. It has been proposed to improve target detection in sea-clutter by the use of two channels operating on a different frequency. It is desirable that the samples are obtained with a time difference of 10 milliseconds or greater in order to achieve the best chance of sea-clutter decorrelation. To meet this objective, experimental equipment has been made using a high aerial rotation speed of about 600 rpm so that the time difference between successive scans of the aerial is of the order of 100 milliseconds. With such equipment, picture storage has been carried out making use of the phosphor on a cathode ray tube to give a storage over the time period of 100 milliseconds. The display repetition rate however of 10 Hz gives a flicker which makes the use of a camera or some other form of scan converter desirable. The main objections however to such techniques lie in the danger and problems of the high aerial rotation speed.